Image display devices such as cathode-ray tube (CRT) display devices, liquid crystal displays (LCDs), plasma display panels (PDPs), electroluminescence displays (ELDs), OLEDs, touch panels, electronic paper, and tablet computers are generally provided with an optical layered body for antireflection on the outermost surface. Such an antireflection optical layered body suppresses reflection of images and decreases reflectivity, by scattering light or interfering with light.
A hard coat film including a transparent substrate and a hard coat layer formed on the surface of the transparent substrate is known as an optical layered body (see Patent Literatures 1 and 2).
Such a hard coat film needs to have enough strength to be used as a product. Specifically, a hard coat film with a hardness of “H” or harder, which is determined by the pencil hardness test specified in JIS K 5600-5-4 (1999), is desirable.
Patent Literature 3 discloses, for example, a hard coated article including a hard coat layer having a thickness of 15 μm or larger and 200 μm or smaller, and a substrate. The hard coat layer is obtainable by applying a curable composition that includes a compound containing three or more ethylenically unsaturated groups and one or more isocyanurate rings within the same molecular on the substrate, and curing the curable composition.
A hard coat film is formed on the outermost surface of an image display device as described above. Therefore, a hard coat film needs to have restorability, which is an ability to restore the surface to its original flat surface when a depression is formed on the surface of a hard coat film by pencils or the like.
Particularly, a hard coat film is subjected to a pencil hardness test in order to confirm whether the film has enough hardness to be used as a product. In the pencil hardness test, a pencil may make a depression on the hard coat film. Therefore, if the hard coat film has insufficient restorability, it cannot be used as a product after the pencil hardness test.
In recent years, a hard coat film having higher hardness tends to be needed, and a hard coat film having high hardness as well as excellent restorability tends to be needed.